The objectives of this project are to investigate the normal neural mechanisms involved in binaural listening and related hearing phenomena. Cats with experimental lesions of the neocortical auditory centers, and human patients with temporal lobe (auditory) injury or disease are being tested on a series of special tests of binaural hearing, including binaural masking-level differences and the precedence effect phenomenon in sound localization. Observed changes or abnormalities in the test performance of these subjects will be used to derive hypothesis as to normal cortical function. In addition, we are also currently, using the gerbil as the experimental model, investigating the effects of early monaural sound deprivation on adult sound localization performance.